Research relating to the present invention was partially supported by grant 000545 from the American Foundation for AIDS Research.
Abbreviations used herein include:
N.sup.4 -SM: N.sup.4 -sulfonamidoyl determinant SMX: Sulfamethoxazole SMX-HD: N.sup.4 -sulfamethoxazoyl-L-histidine SMX-HSA: N.sup.4 -sulfamethoxazoyl-human serum albumin BSA: Bovine serum albumin SM: Sulfonamide TM: Trimethoprim IH: Immediate hypersensitivity
Literature citations in the following descriptions are listed at the end of the specification and are incorporated in pertinent part by reference herein for the reasons cited.
Therapy with SM is accompanied by cutaneous, gastrointestinal, renal, hepatic, or hematologic complications in up to 10% of cases.sup.1-3 despite the recent avoidance of topical administration of SM and the use of lower doses of SM when doses are combined with TM. Many of the adverse reactions to SM are believed to be immunologically mediated. .sup.1-14 Some of the reactions reported have clinical characteristics of anaphylaxis, urticaria, angioedema, serum sickness, contact sensitivity, and photoallergic reactions; each form suggesting that classic immunopathologic mechanisms may have been active..sup.1-14 Cutaneous eruptions occur in 1% to 2% of patients who receive SM alone and in approximately 6% of patients who receive TM/SM combinations..sup.2,3 Pruritic rashes typical of IgE-mediated reactions comprise a significant fraction of the adverse reactions to SM. These problems are increasingly important in the context of expanding clinical use of SM, particularly in combination with TM or erythromycin..sup.9
The immunochemistry of SM allergy in man is not completely understood. Haptenation of human molecules by SM.sup.10 or metabolism followed by haptenation.sup.5,11 has been suspected for many years but never has been unequivocally proven. Reactivity to the para-aminophenyl substituent, to determinants derived from quinone metabolites, and to the SM substituent have been proposed to explain experimental and clinical observations..sup.5,10,11 IgE antibodies to SM were documented nearly 40 years ago by Sherman and Cooke.sup.10 in convincing passive transfer experiments, but the determinants recognized by the IgE were not delineated. Studies of human contact sensitivity to SM, as assessed by patch testing.sup.5,11,12 and lymphocyte transformation assaysl.sup.3,14 have provided insights into the presence and specificity of what appear to be lymphocytemediated reactions. Evidence of immunopathologic reactions to SM abounds, but systematic studies of human immune responses to SM clearly are needed to improve diagnosis and knowledge of the pathophysiology of SM allergy.
Experiments described were designed to explore the possibility that in vivo conjugation of SM via the N.sup.4 -para-amino group or the adjacent benzyl substituent leads to the formation of immunogenic and pathogenic drugcarrier conjugates. Human IgE to SM was detected by use of SMX linked to cellulose via the N.sup.4 -amino group. Inhibition studies indicated that at least some of the antibodies bound free, unmodified SM. These experiments suggested that patients who experience immediate hypersensitivity-like reactions to SM often express IgE to an SM determinant that closely resembles the native drug bound to a carrier by some form of linkage through or near the N.sup.4 -amino group..sup.15
The hypothesis has been tested that patients who experience immediate hypersensitivity reactions to sulfonamides (SM) express IgE that can bind to a N.sup.4 -sulfonamidoyl determinant (N.sup.4 -SM). Sulfamethoxazole (SMX) was coupled to CNBr-activated cellulose disks to form a matrix predominantly substituted with isourea-linked N.sup.4 -SMX determinants. After incubation of human sera with these disks or bovine serum albumin substituted disks as a control, the binding of IgE was assessed with .sup.125 I-labeled antihuman IgE. The binding ratios (counts per minute SMX disks per counts per minute bovine serum albumin disks) for sera from nonallergic donors and newborn infants averaged 1.11 (.+-.0.21SD). Sera from 10 patients with histories of apparent immediate hypersensitivity reactions to SM were studied. Ratios .gtoreq.2.1 (&gt;4 SD above control) were detected in 70% (seven of 10). Significant binding was detected in the sera of three of seven patients with other forms of SM allergy. Preincubation with SMX (80 mmol/L) inhibited binding 7% to 35% in eight of the 10 positive sera tested. Binding of one highly reactive serum was significantly inhibited by SMX, sulfamethizole, and sulfamerazine, but not sulfanilic acid or Trimethoprim. The results of this study suggested that N.sup.4 -SM is a major determinant recognized by IgE to SM and that an in vitro assay capable of detecting IgE to SM has been developed..sup.15